Keyboard system for metallic circuits



(No Model.) ,A

J. A. SEELY.

KBYBUARD SYSTEM P0P. METALLIC. GIRGUlTs. No. 476,494. Patented June '7, 1892.

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vented.

UNTTED STATES PATENT OFFICE.

JOHN A. SEELY, OF NE YORK, N. Y., ASSIGNOR TO THE IVESTERN ELECTRIC COMPANY, OF CHICAGO, ILLINOIS.

KEYBOARD SYSTEM FOR METALLIC CIRCUITS.

SPECIFICATION forming part of Letters Patent No. 476,494, dated .3' une 7, 1892,

Application Bled November 15, 1886.

.To a/ZZ whom it may concern:

Be it known that I, JOHN A. SEELY, a citizen of the United States, residing at New York, in the county of New York and State of New York, have invented a certain new and useful Improvement in Keyboard Systems for Metallic Circuits, (Case No. 3,) of which the following is a full, clear, concise, and exact description, reference beinghad to the accompanying drawngs, torminga part of this speciiication.

My invention relates to the central-office switching apparatus ota telephone-exchange, in which the subscribers are provided with metallic circuits.

My invention was designed more especially for use as a keyboard system for multiple switchboards; but it is evident that it may be used in connection with standard orsingle switchboards.

The object of my invention is to connect the clearing-out annunciator in the circuit of one of the cords in such manner that no currentwll be sent through said clearing-out shutter when a signal of the generator is sent over the line.

My invention will be readily understood by reference to the accompanying drawingsJ in which- Figure l is a sectional View of a switchboard and keyboard with a diagram of the circuits and connections which I have in- Fig. 2 is a detailed sectional View of one of the spring-jacks with a plug inserted therein.

Like parts are indicated by similar' letters of reference throughout the diierent figures.

As shown in Fig. 2, the telephone-line d is connected with the lever b of the spring-jack, andthence normally the circuit may be traced to ground-point c. The other wire d of the metallic circuit is connected with the insulated frame e.

In multiple-switchboard systems a testpoint f is provided near each switch on each board, the different test-points f of any board being connected together by the test-wire of said line. By means of a key g, operated by the lever ZJ, when the lever is lifted from the ground-contact point the test-piecef is closed to said ground-contact point, so that the test- Serial No. 218,948. (No model.)

wire is provided with a ground connection. The test-wire and key g, forming no part of my invention herein, will not be further described, their object being well known in connection with multiple-switchboard systems. Then the plug is inserted, the point h connects with the switch-lever b and the insulated sleeve z' connects with the frame or insulated tube of the spring-jack. Strand 7a of 6o the cord is thus connected through the medium of the tip of the plug and spring Z2 with wire a. Moreover, strand Z of the cord is connected through the medium of the sleeve QI and the frame e with the wire d. W'hen the 65 other plug of the pair rests upon the metallic plate m, the two lstrands are connected together, since the strands Z k are each provided with a separate point or connection upon the heel of the plug, and when these points rest 7o upon a common plate m it is evident that the two strands will be connected. When, however, the other plug of the pair is inserted in the spring-jack of another line, the different strands of the cord will be connected with the different wires of the metallic circuit of the other line, and thus the two lines will be looped together. By means of the callingkeys n o the generator p may be connected or looped into either one of two connected lines; 8o butin neither case will current be sent through the clearing-out drop q. It should be noted that the two upper springs of the calling-keys o n are placed above a common contact, which is connected to one pole of the calling-generator p, while the other pole of the generator is connected with a contact common to the other or lower corresponding springs of said calling-keysa Therefore when either callingkey is depressed the generator will be brought 9o into circuit between the springs or levers thereof. When the cam-lever r is thrown down, as shown, the telephone is disconnected from the circuit while the lines remain connected together. On throwing the cam-lever r up the plunger of the listeningkey is raised so that the springs of the calling-key, closed upon the points of the key, connect with the telephone. Thus the telephone may be brought into the circuit of the roo strand of the cord which connects the tips of the two plugs together.

Having thus described my invention, I claim as new and desire to secure by Letters Patentl. In a keyboard syst-ein, the combination of calling-keys composed each of two levers, a pair of cords having two strands, the two strands being connected to the levers of the calling-keys, respectively, contact-points connecting with the calling-generator, a clearingout annunciator permanently included in a circuit between corresponding levers or springs of the keys, whereby the generator may be looped into the circuit of either of the two telephone-lines, while at the saine time the clearing-out anuunciator is excluded from the circuit. 

